US9712043B2 - Apparatus and method for controlling overcurrent of grid-connected inverter due to abnormal grid voltage - Google Patents

Apparatus and method for controlling overcurrent of grid-connected inverter due to abnormal grid voltage Download PDF

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Publication number
US9712043B2
US9712043B2 US14/899,015 US201414899015A US9712043B2 US 9712043 B2 US9712043 B2 US 9712043B2 US 201414899015 A US201414899015 A US 201414899015A US 9712043 B2 US9712043 B2 US 9712043B2
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Prior art keywords
grid
output current
voltage variation
axis voltage
value
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US20160126828A1 (en
Inventor
Jeong Heum Lee
Sang Ho Moon
Ju Young Chang
Jae Sig Kim
Jin Su Lee
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Korea Fuel Cell Co Ltd
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Posco Energy Co Ltd
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Assigned to POSCO ENERGY CO., LTD. reassignment POSCO ENERGY CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Chang, Ju Young, KIM, JAE SIG, LEE, JEONG HEUM, LEE, JIN SU, MOON, SANG HO
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Assigned to KOREA FUEL CELL CO., LTD. reassignment KOREA FUEL CELL CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: POSCO ENERGY CO., LTD.
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/122—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
    • H02M2001/325—

Definitions

  • the presently disclosed embodiment relates to controlling of an overcurrent of a grid-connected inverter, and a technology for preventing overcurrent of a grid-connected inverter when an abnormal grid voltage occurs.
  • a grid-connected inverter In general, a grid-connected inverter generates power in synchronization with an output current reference value. However, if an instant low voltage occurs in a grid, a difference generates between an output voltage of the grid-connected inverter and a grid voltage, and accordingly, an input current of the grid-connected inverter varies rapidly. Due to the above rapid variation in the current, an overcurrent trip occurs in the grid-connected inverter.
  • the presently disclosed embodiment provides an apparatus and method of controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage, which is capable of reducing an output current before an output current rapidly varies, by detecting a rapid variation in a grid voltage.
  • an apparatus of controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage including: a grid voltage sensor configured to sense a grid voltage according to an output current of the grid-connected inverter; a voltage variation calculator configured to calculate a D-axis voltage and a Q-axis voltage of the grid voltage to obtain variation values of the D-axis voltage and the Q-axis voltage; and an output current controller configured to determine whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds a set value of the grid voltage variation, and decrease the output current by a predetermined value when one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.
  • the output current controller may determine whether a greater value between the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.
  • the apparatus may further include a timer configured to count a predetermined time period after decreasing the output current by the predetermined value, wherein the output current controller may determine whether the predetermined time period has passed, and return the output current that has decreased to the output current of an original magnitude.
  • a method of controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage including: sensing a grid voltage by a grid voltage sensor according to an output current of the grid-connected inverter; calculating a D-axis voltage variation value and a Q-axis voltage variation value by calculating a D-axis voltage and a Q-axis voltage by a voltage variation calculator; determining whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds a set value of the grid voltage variation by using an output current controller; and when one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation, decreasing the output current by a predetermined value by using the output current controller.
  • the determining of whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation may determine whether a greater value between the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation by using the output current controller.
  • the method may further include determining whether a predetermined time period has passed after decreasing the output current by the predetermined value by using a timer; and when the predetermined time period has passed, returning the output current that has decreased to the output current of an original magnitude by using the output current controller.
  • an output current of a grid-connected inverter is reduced by detecting a rapid variation in a grid voltage, thereby preventing trips of the grid-connected inverter due to overcurrent.
  • FIG. 1 is a block diagram of an apparatus for controlling overcurrent of a grid-connected inverter due to abnormal grid voltage according to an aspect of the presently disclosed embodiment
  • FIG. 2 is a graph showing a reduction in an output current according to the apparatus for controlling overcurrent of the grid-connected inverter of FIG. 1 ;
  • FIG. 3 is a flowchart illustrating a method of controlling overcurrent of a grid-connected inverter due to abnormal grid voltage according to an aspect of the presently disclosed embodiment.
  • FIG. 1 is a block diagram of an apparatus for controlling overcurrent of a grid-connected inverter due to abnormal grid voltage, according to an aspect of the presently disclosed embodiment.
  • the apparatus includes a grid-connected inverter 100 , a grid voltage sensor 110 , a voltage variation value calculator 120 , an output current controller 130 , and a timer 140 .
  • the grid-connected inverter 100 is an inverter connected to a power grid in order to supply electric power to a grid.
  • a direct current (DC) electric power input via an input terminal IN is converted to an alternating current (AC) electric power in the grid-connected inverter 100 , and is supplied to the power grid via an output terminal OUT.
  • DC direct current
  • AC alternating current
  • the grid voltage sensor 110 senses a grid voltage output through the power grid, and outputs a sensing result to the voltage variation value calculator 120 .
  • the grid voltage sensor 110 includes a voltage measuring sensor for sensing the grid voltage.
  • the voltage variation value calculator 120 calculates a D-axis voltage and a Q-axis voltage of the grid voltage sensed by the grid voltage sensor 110 to produce variation values of the D-axis voltage and the Q-axis voltage, and outputs the calculation results to the output current controller 130 .
  • the voltage variation value calculator 120 calculates the D-axis voltage and the Q-axis voltage of the grid voltage that is sensed, and calculates a D-axis voltage variation value and a Q-axis variation value per a predetermined sampling time with respect to the calculated D-axis voltage and the Q-axis voltage.
  • the D-axis voltage and the Q-axis voltage are obtained by transforming the grid voltages U, V, and W into a synchronous frame by a frequency of the grid voltage.
  • the Q-axis voltage is a magnitude of the grid voltage and the D-axis voltage is 0.
  • a three-phase grid voltage of 380 V is transformed into the synchronous frame, and then, the Q-axis voltage is 380 V and the D-axis voltage is 0 V.
  • the output current controller 130 determines whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value calculated by the voltage variation value calculator 120 exceeds a set value of the grid voltage variation.
  • the set value of the grid voltage variation denotes a threshold voltage value of a normal variation range for determining abnormality of the grid voltage at every predetermined period (for example, 250 ⁇ sec).
  • the output current controller 130 determines whether a large one between the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.
  • the output current controller 130 controls the grid-connected inverter 100 so as to reduce the output current output from the grid-connected inverter 100 by a predetermined value.
  • FIG. 2 is a graph showing a reduction in the output current by the apparatus for controlling overcurrent of the grid-connected inverter shown in FIG. 1 .
  • the output current controller 130 controls the grid-connected inverter 100 so as to reduce the magnitude of the output current, which has been suddenly increased, to a predetermined value or less. Accordingly, the grid-connected inverter 100 outputs the output current that has reduced to a predetermined value or less.
  • the output current controller 130 controls the timer 140 to start the timing operation when the output current decreases to a predetermined value or less.
  • the timer 140 counts a time period according to the timing start command of the output current controller 130 . After that, the output current controller 130 determines whether the time period counted by the timer 140 has passed a predetermined time (e.g., 100 ms).
  • a predetermined time e.g. 100 ms.
  • the predetermined time denotes a sufficient time to address the abnormal grid voltage.
  • the output current controller 130 controls the grid-connected inverter 100 to output the output current of an original magnitude from the output current. Accordingly, the grid-connected inverter 100 outputs the output current of the original magnitude.
  • FIG. 3 is a flowchart illustrating a method of controlling overcurrent of the grid-connected inverter due to the abnormal grid voltage, according to an aspect of the presently disclosed embodiment.
  • the grid voltage sensor 110 senses a grid voltage according to the output voltage from the grid-connected inverter 100 (S 200 ).
  • the voltage variation calculator 120 calculates a D-axis voltage and Q-axis voltage of the grid voltage sensed by the grid voltage sensor 110 , and calculates variation values of the D-axis current and the Q-axis current (S 202 ).
  • the voltage variation calculator 120 calculates the variation value of the D-axis voltage and the variation value of the Q-axis voltage per unit sampling time period with respect to the D-axis and Q-axis voltages of the grid voltage.
  • the output current controller 130 determined whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value calculated by the voltage variation calculator 120 exceeds a set value of the grid voltage variation (S 204 ).
  • the set value of the grid voltage variation denotes a threshold voltage value of a normal variation range for determining abnormality of the grid voltage at a predetermined period (e.g., 250 ⁇ m).
  • the output current controller 130 exceeds whether a greater value between the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.
  • the output current controller 130 decreases the output current output from the grid-connected inverter 100 by a predetermined value, when one of the D-axis and Q-axis variation values exceeds the set value of the grid voltage variation (S 206 ).
  • the output current controller 130 controls the grid-connected inverter 100 to decrease to a predetermined value or less, and accordingly, the grid-connected inverter 100 outputs the output current that has decreased to the predetermined value or less.
  • the output current controller 130 determines whether a predetermined time period has passed after decreasing the output current by the predetermined value (S 208 ).
  • the predetermined time period denotes a sufficient time for addressing the abnormality of the grid voltage.
  • the output current controller 130 After operation S 208 , when the predetermined time period has passed, the output current controller 130 returns the decreased output current to the output current of an original magnitude (S 210 ). If the predetermined time period has passed, the output current controller 130 controls the grid-connected inverter 100 to output the output current of the original magnitude from the decreased output current, and accordingly, the grid-connected inverter 100 outputs the output current of the original magnitude.
  • the method according to one or more aspects of the presently disclosed embodiment can also be implemented through computer readable code/instructions in/on a medium, e.g., a computer readable medium, to control at least one processing element to implement any above described aspect.
  • a medium e.g., a computer readable medium
  • the method may be implemented in a universal digital computer operating the codes/instructions/programs by using a computer readable recording medium.
  • the computer-readable recording medium are magnetic storage media (e.g., ROM, floppy disks, hard disks, magnetic tapes, etc.) and optical recording media (e.g., CD-ROMs, or DVDs).

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
US14/899,015 2013-06-26 2014-06-20 Apparatus and method for controlling overcurrent of grid-connected inverter due to abnormal grid voltage Active US9712043B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR10-2013-0073772 2013-06-26
KR1020130073772A KR101493511B1 (ko) 2013-06-26 2013-06-26 계통 전압 이상에 따른 계통 연계 인버터의 과전류 억제장치 및 방법
PCT/KR2014/005458 WO2014208932A1 (ko) 2013-06-26 2014-06-20 계통 전압 이상에 따른 계통 연계 인버터의 과전류 억제장치 및 방법

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US20160126828A1 US20160126828A1 (en) 2016-05-05
US9712043B2 true US9712043B2 (en) 2017-07-18

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US (1) US9712043B2 (zh)
EP (1) EP3016257B1 (zh)
JP (1) JP6247755B2 (zh)
KR (1) KR101493511B1 (zh)
CN (1) CN105340161B (zh)
WO (1) WO2014208932A1 (zh)

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KR101556352B1 (ko) * 2013-06-26 2015-10-01 포스코에너지 주식회사 계통 저전압 발생에 따른 계통 연계 인버터의 보호장치 및 방법
CN107294066B (zh) * 2016-03-30 2019-08-13 比亚迪股份有限公司 逆变器的保护方法、装置和电动汽车
CN113629665B (zh) * 2021-09-02 2024-08-09 武汉船用电力推进装置研究所（中国船舶重工集团公司第七一二研究所） 一种三相逆变电源短路自恢复方法

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05252751A (ja) 1992-03-02 1993-09-28 Hitachi Ltd 自励式電力変換装置の制御装置
JP2000333473A (ja) 1999-05-24 2000-11-30 Matsushita Electric Ind Co Ltd 系統連系インバータ装置
JP2001136664A (ja) 1999-11-05 2001-05-18 Hitachi Ltd 分散形発電システム
US6642689B2 (en) * 2001-02-13 2003-11-04 Hitachi, Ltd. Control apparatus for power converter
US6700400B2 (en) * 2000-12-27 2004-03-02 Honda Giken Kogyo Kabushiki Kaisha Constant detecting apparatus for brushless DC motor, control apparatus for brushless DC motor, and program for detecting constant of brushless DC motor
JP2004153957A (ja) 2002-10-31 2004-05-27 Hitachi Ltd 電力変換装置
US7521887B2 (en) * 2005-12-02 2009-04-21 Hitachi, Ltd. Vector controller for a permanent magnet synchronous motor, inverter module, and permanent magnet synchronous motor constant display system
US8159161B2 (en) * 2008-08-20 2012-04-17 Sanyo Electric Co., Ltd. Motor control device
US20120200243A1 (en) * 2009-12-08 2012-08-09 Mitsubishi Electric Corporation Power conversion device
US20130051103A1 (en) 2011-08-30 2013-02-28 Rolls-Royce Plc Method of controlling an inverter and a controller for controlling an inverter
CN103163363A (zh) 2013-03-11 2013-06-19 西安交通大学 用于动态电压恢复器的电网电压跌落检测算法
US20130335041A1 (en) * 2012-06-19 2013-12-19 Samsung Electronics Co., Ltd. Power conversion apparatus and method of controlling the same
US20140265951A1 (en) * 2013-03-12 2014-09-18 Steering Solutions Ip Holding Corporation Motor control system for determining a reference d-axis current and a q-axis current

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102324865B (zh) * 2011-09-23 2014-04-16 武汉新能源接入装备与技术研究院有限公司 一种光伏并网发电系统中三相变流器的控制方法

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05252751A (ja) 1992-03-02 1993-09-28 Hitachi Ltd 自励式電力変換装置の制御装置
JP2000333473A (ja) 1999-05-24 2000-11-30 Matsushita Electric Ind Co Ltd 系統連系インバータ装置
JP2001136664A (ja) 1999-11-05 2001-05-18 Hitachi Ltd 分散形発電システム
US6700400B2 (en) * 2000-12-27 2004-03-02 Honda Giken Kogyo Kabushiki Kaisha Constant detecting apparatus for brushless DC motor, control apparatus for brushless DC motor, and program for detecting constant of brushless DC motor
US6642689B2 (en) * 2001-02-13 2003-11-04 Hitachi, Ltd. Control apparatus for power converter
JP2004153957A (ja) 2002-10-31 2004-05-27 Hitachi Ltd 電力変換装置
US7521887B2 (en) * 2005-12-02 2009-04-21 Hitachi, Ltd. Vector controller for a permanent magnet synchronous motor, inverter module, and permanent magnet synchronous motor constant display system
US8159161B2 (en) * 2008-08-20 2012-04-17 Sanyo Electric Co., Ltd. Motor control device
US20120200243A1 (en) * 2009-12-08 2012-08-09 Mitsubishi Electric Corporation Power conversion device
US20130051103A1 (en) 2011-08-30 2013-02-28 Rolls-Royce Plc Method of controlling an inverter and a controller for controlling an inverter
US20130335041A1 (en) * 2012-06-19 2013-12-19 Samsung Electronics Co., Ltd. Power conversion apparatus and method of controlling the same
CN103163363A (zh) 2013-03-11 2013-06-19 西安交通大学 用于动态电压恢复器的电网电压跌落检测算法
US20140265951A1 (en) * 2013-03-12 2014-09-18 Steering Solutions Ip Holding Corporation Motor control system for determining a reference d-axis current and a q-axis current

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
European Supplementary Search Report, European Application No. 14818167, dated Apr. 12, 2017.
International Search Report, International Application No. PCT/KR2014/005458, dated Aug. 25, 2014.

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Publication number Publication date
EP3016257A1 (en) 2016-05-04
US20160126828A1 (en) 2016-05-05
CN105340161A (zh) 2016-02-17
EP3016257B1 (en) 2020-02-05
KR20150002921A (ko) 2015-01-08
KR101493511B1 (ko) 2015-02-16
WO2014208932A1 (ko) 2014-12-31
CN105340161B (zh) 2018-01-02
JP2016524449A (ja) 2016-08-12
EP3016257A4 (en) 2017-05-10
JP6247755B2 (ja) 2017-12-13

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